A semi-purified peptide mixture consisting in benzylated derivatives of the CD4-derived peptide TYICEVEDQKEE has been further characterized as an HIV anti-infective, anti-cytopathic and virustatic agent in vitro, at a nominal concentration if 18-32muM. Purified and fully characterized derivatives of TYICEVEDQKEE have been identified which are anti-infective and anti-cytopathic at 40- 80muM, but are less potent virustatic agents. One if these has been synthesized in largescale (10-20 gm), partially purified and characterized, and will be injected into three rhesus macaque monkeys inoculated with the simian immunodeficiency virus B670 as a preliminary test of its anti-viral efficacy and safety in primates in vivo.